Motor vehicle air-conditioning installation equipped with an electronic control device

ABSTRACT

The invention proposes an air conditioning installation furnished with an injection computer ( 42 ), with an air conditioning apparatus and with an electronic control device ( 401 ). The installation furthermore comprises measurement facilities making it possible to establish values relating to the temperature of the external air stream at the inlet of the condenser, to the pressure at the outlet of the compressor ( 123 ), and to the pressure at the inlet of the compressor ( 122 ). The electronic control device ( 401 ) implements the solving of a linear equation, relating the mass flow rate of the refrigerant to the values measured by the measurement facilities so as to calculate an estimate of a quantity relating to the refrigerant. On the basis of this quantity, the electronic device can estimate the power absorbed by the compressor ( 14 ).

The invention relates to the air conditioning circuits of enginedvehicles.

In conventional engined vehicles, the compressor of the air conditioningcircuit is driven by the engine and therefore consumes a part of thepower of the engine. Although the power absorbed by the compressor, whenit is running, is not significant, it nevertheless influences theefficiency of the engine. By decreasing the efficiency of the engine,the power actually absorbed by the compressor increases the consumptionof fuel and the pollution generated by the vehicle's exhaust gases.

To optimize the efficiency of the engine, one solution consists inestimating the instantaneous power actually absorbed by the compressor.Knowledge of this information makes it possible, in fact, to adapt theinjection parameters of the engine to the actual requirements. In theabsence of this information, the injection computer chooses, by default,injection parameters corresponding to the maximum value of the powerabsorbed, which value is rarely attained in practice.

This drawback may be of concern to internally controlled mechanicalcompressors which operate by way of the clutch coupling interposedbetween the engine and the compressor. In regulated mode, the internallycontrolled compressors adapt their volumetric capacity according to alinear law connecting the value of the pressure at the inlet of thecompressor, the so-called low pressure, to the compressor outlet value,the so-called high pressure. Nevertheless, it may happen that the poweractually absorbed by the compressor is less than its nominal power.

Such compressors absorb a power which depends on the operatingconditions and which cannot therefore be reduced, even if the poweractually absorbed by the compressor is known. On the other hand, it ispossible to regulate the operation of the air conditioning by decouplingthe compressor when the power is not acceptable.

This drawback is an even greater impediment in respect of externallycontrolled compressors, the use of which is generalized.

Specifically, in externally controlled mechanical compressors, the poweractually absorbed by the compressor is often less than its nominalpower. Subsequently, the injection must compensate for the discrepancybetween the nominal mechanical power and the mechanical power actuallyabsorbed, thereby decreasing the efficiency of the engine.

In known embodiments, use is made of a map which provides an estimate ofthe instantaneous power absorbed by the compressor as a function of theinstantaneous value of the high pressure measured by a first sensor andof an information item relating to the operation of the vehicle andmeasured by a second sensor. This device is an empirical device which isbased on a map which is established using tests and is installed in theair conditioning computer.

This method has the drawback of not taking all the possible cases intoaccount and therefore remains approximate.

In the case of electric compressors, the instantaneous value of thepower absorbed by the compressor is easily available since thevolumetric capacity of these compressors—and hence the mass flow rate ofthe refrigerant absorbed—is known. However, for compressors of thistype, the problem arises of anticipating the overshoot of the maximumelectric power absorbed by the compressor as the speed of rotation ofthe compressor increases. Specifically, if the existing embodiments makeit possible to know the instantaneous value of the electric powerconsumed, they do not make is possible to forecast the value that thispower will take as a function of the alterations in the speed ofrotation. This inability to forecast the threshold of overshoot of thiscritical speed of the compressor permits a posteriori solutions only.One of these solutions consists in triggering the internal safetyfeature of the engine so as to limit the power absorbed by thecompressor and hence the speed.

Most of the existing embodiments use empirical methods to adjust thepower absorbed by the compressor. However, it had been thought that asimple relation existed between the high pressure and the power absorbedby the compressor. Nevertheless, a device based on such a relation hasnot been produced.

It is an aim of the present invention to propose a device making itpossible to provide an estimate of the power absorbed, on the basis of asimple relation between the mass flow rate of the refrigerant at thehigh pressure.

It is a further aim of the present invention to provide such a devicecapable of obtaining an estimate of correct accuracy.

To this end the invention proposes an air conditioning installation forvehicle with engine furnished with an injection computer. Theinstallation comprises a refrigerant closed circuit comprising acompressor, a condenser, a relief valve and an evaporator, the condenserreceiving a stream of air passing through an electric fan assembly, aswell as an electronic control device intended to interact with therefrigerant closed circuit and the injection computer.

Advantageously, the installation comprises measurement facilities makingit possible to establish:

-   -   a first value relating to the temperature of the external air        stream at the inlet of the condenser,    -   a second value relating to the pressure at the outlet of the        compressor, termed the high pressure,    -   a third value relating to the pressure at the inlet of the        compressor, termed the low pressure,        the electronic control device being able to implement the        solving of a linear equation, relating the mass flow rate of the        refrigerant to the values measured by the first and the second        measurement facility so as to calculate an estimate of a        quantity relating to the refrigerant and to estimate, on the        basis of this quantity, of the measurements delivered by said        measurement facilities and of the information items transmitted        by the injection computer, the power absorbed by the compressor.

In one form of embodiment, the compressor is a mechanical compressor andthe quantity calculated by the electronic control device is the massflow rate of the refrigerant.

In another form of embodiment, the compressor is an electricalcompressor and the quantity calculated by the electronic control deviceis the high pressure of the refrigerant.

According to the first form of embodiment, the electronic control deviceis able to calculate an estimate of the mass flow rate of therefrigerant on the basis of the values measured by the first and thesecond measurement facility and of two information items relating to theoperation of the vehicle, that are transmitted by the injectioncomputer.

Advantageously, the electronic control device is also able to calculatethe power absorbed by the compressor on the basis of the calculatedestimate of the mass flow rate, of the values measured by the second andthe third measurement facility, and of information items relating to theoperation of the vehicle, that are delivered by the injection computer.

In the second form of embodiment according to the invention, theelectronic control device is able to calculate an estimate of the highpressure of the refrigerant on the basis of the value measured by thefirst measurement facility, of the value of the mass flow rate of therefrigerant and of two information items relating to the operation ofthe vehicle, that are transmitted by the injection computer.

Advantageously, the electronic control device is able to calculate thepower absorbed by the compressor on the basis of the estimate of thehigh pressure calculated, of the value measured by the third measurementfacility, and of information items relating to the operation of thevehicle, that are delivered by the injection computer.

As a supplement, according to this second form of embodiment, theelectronic control device is capable, for a given starting state, ofiteratively calculating values of the power absorbed by the compressor,on the basis of values of the high pressure corresponding to smallchosen variations of the speed of rotation so as to estimate the maximumspeed of rotation.

The invention also covers a program product, which may be defined ascomprising the functions for solving said equation so as to estimate thepower absorbed by the air conditioner.

Other characteristics and advantages of the invention will becomeapparent on examining the detailed description hereinafter, and theappended drawings in which:

FIG. 1 represents an overall view of an air conditioning deviceinstalled on board a vehicle,

FIG. 2 is a diagram of a motor vehicle installation with enginefurnished with a control device according to a first form of embodimentof the invention,

FIG. 3 is a view similar to FIG. 2 in a variant embodiment,

FIG. 4 illustrates the accuracy of estimation of the mass flow rateaccording to the invention,

FIG. 5 illustrates the relation between the speed of the air and thespeed of the vehicle,

FIG. 6 is a chart illustrating the accuracy of estimation of the powerabsorbed by the air conditioning, according to the invention,

FIG. 7 represents a block diagram of an electric compressor, and

FIG. 8 is an exemplary flowchart of anticipation of command of speed ofrotation.

Annex A comprises the main mathematical equations used in theinstallation.

The drawings contain, in essence, elements of definite nature. Theyshall therefore be able not only to serve to better elucidate thedescription, but also to contribute to the definition of the invention,as the case may be.

We refer firstly to FIG. 1 which represents an overall view of an airconditioning apparatus built into a vehicle. The air conditioningapparatus comprises a refrigerant closed circuit whose refrigerant maybe any subcritical fluid, that is to say any fluid having a criticaltemperature above the temperature of the hot source. The airconditioning apparatus also comprises a compressor 14, a condenser 11, adesiccant tank 18, a relief valve 12 and an evaporator 13, traversed inthis order by the refrigerant. The following description will be givenchiefly with reference to the refrigerant R134a by way of nonlimitingexample.

The condenser 11 receives an external air stream 16 so as to remove theheat drawn off from the cabin, which under certain operating conditionsis set into motion by an electric fan assembly 15.

The evaporator 13 receives an air stream from a blower 20 supplied withan external air stream 18 and produces an air-conditioned stream 21which is sent to the cabin of the vehicle.

FIG. 2 represents the installation, according to the present invention,set in place in a motor vehicle, possibly in motion with a forward speedVa. The motor vehicle is propelled by an engine 43, controlled by aninjection computer 42. The computer receives information from varioussensors which it interprets in order to adjust the parameters. It cantherefore provide information 33 regarding instantaneous values relatingto the operation of the vehicle, and especially the forward speed of thevehicle, the temperature of the external air entering the airconditioning apparatus, the speed of rotation of the compressor and thevoltage of the electric fan assembly.

The vehicle is also equipped with the air conditioning apparatus 10described above, represented diagrammatically in FIG. 2. Moreover, theinstallation comprises a cabin regulator 41 intended to fix thetemperature preset of the external air 18 blown to the inlet of theevaporator 11.

The engine injection computer can act on the air conditioning apparatusby virtue of an air conditioning regulator 402. Using this link it ispossible only to turn on or turn off the air conditioning apparatusaccording to the conditions related to the operation of the engine or tothe external commands. For example, it makes it possible to prevent theair conditioning apparatus from being turned on when the engine isheavily loaded.

This link 402 is limited to this “all or nothing” mode of operation. Inthe absence of a device for instantaneously estimating the powerabsorbed by a mechanical compressor, or for estimating by anticipationthe power absorbed by an electric compressor, the air conditioningregulator 402 may not adjust the operation of the air conditioning loop.

The Applicant has set in place such a device making it possible toimprove this manner of operation, through the use of a simple relation,obtained from the laws of thermodynamics between the mass flow rate ofthe refrigerant and the high pressure.

To do this, the regulator of the cabin 41, the injection computer of theengine 42 and the air conditioning apparatus 10 are linked to anelectronic card 401 for a bi-directional exchange of information.

The electronic card implements the solving of the equations that make itpossible to obtain an estimate of the power absorbed by the compressor.It can transmit information which results from this estimate to theinjection computer, via the link 32.

The electronic card 401 may be regarded as an integral part of the airconditioning regulator 402. The air conditioning regulator 402 has inparticular the role of adapting the amount of heat drawn off from thecabin, the so-called refrigerating power, so as to attain the preset ofair blown to the inlet of the evaporator. This preset is previouslyindicated to the air conditioning regulator 402 by the cabin regulator(link 35).

The electronic card 401 retrieves information 30 originating from thesensors set in place on the air conditioning apparatus. It also receivesinformation from the injection computer of the engine 42 via the link33, in particular the forward speed of the vehicle, the voltage of theelectric fan assembly, the speed of rotation of the compressor or thetemperature of the external air.

The cabin regulator 41 exchanges information with the air conditioningregulator, said information relating to the preset of air blown to theinlet of the evaporator, by means of the links 34 and 35.

The links 30, 33 and 35 of the electronic card 401 with the airconditioning apparatus 10, the injection computer of the engine 42 andthe regulator of the cabin 41 are aimed at determining the instantaneousvalues of the condensation temperature Tk, of the temperature of theexternal air at the inlet of the condenser Taek, of the pressure at theinlet of the compressor, the so-called low pressure LP, of the pressureat the outlet of the compressor, the so-called high pressure HP, of theforward speed of the vehicle Va, of the voltage of the electric fanassembly EFA and of the speed of rotation of the compressor N.

The instantaneous values of HP and Tk being related by the law ofsaturation of fluids, it is sufficient to determine one of these twovalues, the other being deducible by the electronic card by means of therelation in accordance with the law of saturation of fluids.Furthermore, the values of the forward speed of the vehicle Va, of thevoltage of the electric fan assembly EFA and of the speed of rotation ofthe compressor N are data accessible to the injection computer of theengine.

They are therefore transmitted directly by the latter to the electroniccard via the link 33. Several possibilities then exist for providing theelectronic card with the other parameters. In particular, the setting inplace of sensors on the air conditioning apparatus 10 and possibly theuse of additional information originating from the injection computer 42contribute to the obtaining of these parameters.

The simple relation obtained by the Applicant relates more precisely themass flow rate, the high pressure and other parameters relating to theoperation of the air conditioning apparatus and to the operation of thevehicle.

In a first form of embodiment, described hereinafter, a mechanicalcompressor is used. An object of the device according to this first formof embodiment of the invention is to estimate the mass flow rate m ofthe refrigerant passing through the air conditioning circuit and toestimate on the basis of this value the mechanical power Pa absorbed bythe air conditioning loop.

The relation of annex A1 indicates that by knowing the condensationtemperature Tk, the temperature of the external air at the inlet of thecondenser Taek and the constant A, it is possible to estimate the massflow rate m of the refrigerant.

The link 33 from the injection computer of the engine provides theinstantaneous values of the forward speed of the vehicle Va and of thevoltage of the motor fan assembly EFA. These values allow thecalculation of the mass flow rate of the air Cpa and subsequently of theconstant A, having regard to the relation of annex A1 which relates A toCpa (annex A1). FIG. 5 shows in fact that the mass flow rate of the airis related to the forward speed of the vehicle Va and to the voltage ofthe electric fan assembly EFA.

In a particular embodiment, the device comprises two sensors formeasuring the condensation temperature Tk, and the temperature of theexternal air at the inlet of the condenser Taek.

In FIG. 2, the condensation temperature Tk is measured by the sensor 23which is a probe placed at the inlet of the condenser directly withinthe refrigerant. This location is chosen such that the refrigerant is ina liquid/vapor mixture state, for example at the end of the first passof the condenser if the latter contains 4 passes.

As a variant, the condensation temperature Tk may be measuredindirectly. To do this, use is made of the sensor 123 of FIG. 3 whichmeasures the value of the high pressure HP at the outlet of thecompressor. The electronic card 401 will then calculate the value of thecondensation temperature Tk by using the law of saturation of fluids. Inthe embodiments of FIG. 3, the sensor 123 which measures theinstantaneous value of the high pressure HP may be placed at anyappropriate spot between the outlet of the compressor and the inlet ofthe condenser, or preferably between the outlet of the condenser and theinlet of the relief valve.

With reference to FIG. 2, the temperature Taek of the external air atthe inlet of the condenser 11 is measured by the sensor 25 which is atemperature probe placed between the electric fan assembly 15 and thecondenser 11.

In another embodiment, only one sensor is used in the air conditioningcircuit for the estimation of the instantaneous value of the mass flowrate of the refrigerant. This sensor is the sensor 23 (or 123), whichmeasures the instantaneous value of the condensation temperature Tk.

With reference to FIG. 3, the instantaneous value of the temperatureTaek of the external air at the inlet of the condenser (11) is thencalculated by the electronic card, on the basis of the instantaneousvalues of the forward speed Va of the vehicle and of the temperature ofthe external air Text at the inlet of the electric fan assembly, thesebeing provided by the injection computer of the engine 42 and by thecabin regulator 41.

In all these embodiments, the measured or calculated instantaneousvalues of the condensation temperature Tk, and of the temperature of theexternal air at the inlet of the condenser Taek are associated with theconstant A, according to the relation of annex A1, by the electroniccard so as to calculate an estimate of the mass flow rate of refrigerantin the air conditioning circuit.

FIG. 4 illustrates the accuracy of estimation of the mass flow rate ofthe refrigerant flowing around the air conditioning circuit. The graphof FIG. 4 represents the discrepancy between a first curve correspondingto the variations of the estimated mass flow rate of the refrigerantR134a (m134a sim) as a function of time and a second curve correspondingto the variations of the actual mass flow rate of the refrigerant R134a(m134a kg/h) as a function of time.

The graph indicates a smallish discrepancy between the two curves andconsequently satisfactory accuracy. This discrepancy is satisfactory inrespect of the estimate of the power absorbed by the compressor.

Advantageously, the Applicant has found that this estimate of the massflow rate of refrigerant which offers worthwhile accuracy under theconditions stated previously made it possible to calculate themechanical power absorbed by the compressor.

With reference to FIGS. 2 and 3, the device described previously isdevised so as to obtain the information which makes it possible,according to the relations of annexes A2 and A3, to calculate themechanical power absorbed. In addition to the estimate of the mass flowrate, this information pertains to the estimate of the work ofisentropic compression Wis and the speed of rotation of the compressorN. The constants B, C and D and E are related to operating parameters ofthe air conditioning circuit and hence fixed as calculation parameters.

The electronic card 401 estimates the compression ratio Pr on the basisof the values of the high pressure HP and of the low pressure LP, so asto calculate the work of isentropic compression Wis. The high pressureHP has been measured by the device for estimating the mass flow rate,directly or indirectly (through calculation of the condensationtemperature). Moreover, the speed of rotation of the compressor N isdelivered to the electronic card by the injection computer of the engine42 via the link 33 with reference to FIGS. 2 and 3. It remains tomeasure the value of the low pressure LP.

In a variant embodiment with reference to FIG. 2, the instantaneousvalue of the low pressure LP is measured directly by a sensor 22 whichmay be placed at any desired spot between the evaporator and thecompressor. This measurement is transmitted to the electronic card 401,via the link 30.

The instantaneous value of the low pressure LP may also be measuredindirectly. In this case, the sensor is a probe, designated by thereference 122 in FIG. 3, which measures the evaporation temperature. Theevaporation temperature is, in fact, related to the low pressure LP bythe law of saturation of fluids. This probe may be a probe withthermistor, of conventional structure, placed in the vanes of theevaporator.

As a variant, the low pressure could be estimated indirectly on thebasis of the air temperature at the outlet of the evaporator (13), ofthe high pressure HP, of the external air temperature Text and of thevoltage of the blower. The cabin regulator 41 can provide thetemperature preset of the cabin as well as the voltage of the blower soas to calculate an estimate of the air flow rate at the evaporatorlevel. However, this variant has the drawback of being ratherinaccurate.

The probe may furthermore be placed actually within the refrigerant, ina duct or in the relief valve 12 for example.

In this embodiment, the measured value of the evaporation temperature istransmitted to the electronic card (link 30) which applies the law ofsaturation of fluids so as to deduce therefrom the value of the lowpressure LP.

FIG. 6 illustrates the accuracy of measurement of the mechanical poweraccording to this embodiment, during tests carried out for a mass flowrate of the air of 2000 kg/h and of a temperature of the external airTaek of 35° C. The graph shows that the discrepancy between the curverepresenting the estimated mechanical power absorbed by the compressor(Wshaft meas) and the actual mechanical power absorbed by the compressor(Wshaft sim) is smallish, thus indicating satisfactory measurementaccuracy. Nevertheless, this accuracy depends on the quality and on theestimate of Tk and of Taek.

The computer then forwards the estimated value of the mechanical powerabsorbed by the compressor to the injection module of the engine. Thecomputer then adapts the nominal mechanical power absorbed by thecompressor if this power exceeds a maximum value defined by the computeron the basis of this estimated value. Subsequently, the fuel consumptionis reduced and the excessive increases in the power absorbed by thecompressor are better controlled.

In the case of internally controlled mechanical compressors, the deviceaccording to the present invention is likewise used to estimate themechanical power absorbed by the compressor. However, for this type ofcompressor, this estimated power is used to decouple the compressor soas to reduce the mass flow rate of refrigerant absorbed by thecompressor.

In a second embodiment, the compressor is an electric compressor. Anobject of the device according to this second embodiment is to estimatethe high pressure and on the basis of this value to estimate the valueof the electric power absorbed by the compressor.

It is a further aim of this second embodiment to carry out ananticipation of command of speed of rotation.

FIG. 7 represents an electric compressor diagram. The electriccompressor 14 is actuated by an integrated electric motor 140 byappropriate means of command and is supplied from an electric source 142of battery type. This source transmits energy to the compressor via afrequency converter 141.

In electric compressors, the volumetric capacity is fixed, and hence itis simple to ascertain the instantaneous electric power absorbed by thecompressor, in accordance with the equation of annex A4.

Electric compressors comprise limiters of absorbed power so as to cutoff the air conditioning should the instantaneous value of the powerabsorbed be greater than the nominal power. However, these limitersintervene after the nominal power has been attained, and therefore donot anticipate the overshoot.

It is known that the mass flow rate of the fluid varies as a function ofthe speed of rotation. Now, the existing relations do not make itpossible to deduce the electric power absorbed by the compressor otherthan as a function of the variations of the high pressure.

A solution, according to the invention, consists in calculating thevalue of the high pressure on the basis of the variation of the massflow rate so as to estimate the value of the electric power absorbed,within the context of an anticipation.

Advantageously, the Applicant has used the relation of annex A1 whichrelates the mass flow rate of the refrigerant to the parameters relatedto the operation of the air conditioning apparatus and to the operationof the vehicle, to estimate this value of the high pressure HP.

FIGS. 1 to 3 apply likewise to this embodiment.

The electronic card receives the information from the computer 42 andfrom the air conditioning apparatus 10 so as to solve the equation ofannex A1. The computer transmits the value of the mass flow rate of thefluid, the forward speed of the vehicle and the voltage of the electricfan assembly to the electronic card. The air conditioning apparatustransmits the value of the temperature of the air at the inlet of thecondenser Taek, as measured in the manner described previously (FIGS. 2and 3), to the electronic card.

The electronic card can then calculate an estimate of the value of thecondensation temperature Tk according to annex A1. The condensationtemperature Tk being related to the high pressure HP by the law ofsaturation of fluids, the electronic card deduces therefrom, through asimple calculation, the value of the high pressure HP.

The device is then capable of estimating the electric power absorbed bythe compressor, within the context of an anticipation of command ofspeed. With reference to annex A4, the power is related to thecompression ratio, hence to the high pressure HP and to the low pressureLP, as well as to the speed of rotation N of the compressor 14.

The sensor 22 of FIG. 2 (or the sensor 122 of FIG. 3) measures theinstantaneous value of the low pressure and transmits it to theelectronic card (via the link 30). The computer transmits the value ofthe speed of rotation N to the electronic card.

The electronic card can then associate these values with the value ofthe high pressure HP so as to deduce therefrom the value of the electricpower absorbed by the compressor.

In this embodiment, the mechanical power absorbed by an electriccompressor is estimated so as to anticipate the overshoot of a maximumelectric power. Estimation allows the compressor to never attain a zonewhere the effectiveness of the compressor is very poor. Thisanticipation is possible since the device makes it possible to predictthe value of the high pressure that would be obtained by increasing themass flow rate absorbed by the compressor, thereby providing an estimateof the value of the speed of rotation not to be exceeded.

FIG. 8 represents a flowchart of anticipation of command of speed ofrotation. The corresponding equations are indicated, in part, in annexesA4 to A6.

The sensors 22 (or 122) and 23 (or 123) measure initial values of thelow pressure LP0 and of the high pressure HP0 and transmit them to theelectronic card. The injection computer 42 provides the electronic cardwith the values of the speed of rotation N0 and of the mass flow rate ofthe fluid m0. The values HP0, LP0, N0 and m0 are obtained during theinitial step 100. In the course of this step the electronic cardfurthermore calculates the value of the electric power Pel0, on thebasis of Hp0 and Lp0. The electronic card also fixes the value of acoefficient, the so-called relaxation factor α0, at 1. The values HP0,LP0, N0, m0, Pel0 and α0 constitute the initial state.

The flowchart of FIG. 8 is iterative and therefore comprises variousstates labeled by the index j.

In step 102 corresponding to a state j, the card increases the speed ofrotation of the compressor by an amount fixed by the air conditioningregulator, and modulated by the relaxation factor αj-1, as indicated inannex A5.

We then go to step 104 to calculate the corresponding value of the massflow rate mj. It is deduced simply from the variation of the speed ofrotation dNj and from its value Nj calculated in step 102 and from theprevious value of the mass flow rate mj-1 (annex A6).

In step 106, the electronic card can then calculate the new value of thehigh pressure HPj in accordance with the relation of annex A1 and asdescribed hereinabove.

This method of anticipation neglects the variations of the low pressure(LPj=LP0). On the basis of the new value of HPj and of the value of LP,the electronic card calculates, in step 108, the new value of theelectric power Pelj, that is to say, the power that would be attained ifthe speed of rotation were to increase by dNj.

In step 110, the electronic card compares Pelj with the maximum power ofthe compressor. If Pelj is greater than this power, the value of themaximum speed of rotation not to be exceeded is Nj and the iteration isterminated. In the converse case, the electronic card repeats steps 102to 110, after having reduced αj-1 and incremented j. αj is deduced fromαj-1 and from the values of Pelj and Pelj-1, as indicated in annex A5.

The estimate of this speed of rotation is then used to regulate theoperation of the air conditioning.

The anticipation of the command of speed, as described hereinabove, usesat each iteration a variation of the speed of rotation dNj chosen hereby way of example. The invention is not limited to this pace of increaseof the speed of rotation.

Moreover, the present invention is also aimed at the software code thatit involves, most particularly when the latter is made available on anyreadable medium on a computer. The expression “computer readable medium”covers a storage medium, for example magnetic or optical, as well as ameans of transmission, such as a digital or analog signal.

Annex A

A1. Measurement of the Mass Flow Rate of a Refrigerantm=A.(Tk−Taek)A=Ks.[ΔHcdr.(1+Ks/(2.ma.Cpa))]−1A2. Estimation of the Compression Work Delivered by the CompressorWis=B.(Pr(k−1)/k−1)A3. Estimation of the Mechanical Power Absorbed by the Air ConditioningP _(a) =C.m.Wis+D.NWis=E.(Pr(k−1)/k−1)A4. Estimation of the Electric Power Absorbed by the Air ConditioningPel=(Wel)′Wel=(F.Wis+G.N/r)r=F ₁ −F ₂ .Pr−F ₃(N)A5. Variation of the Speed of RotationNj=Nj−1+αj.dN 0αj=αj-1.Pelj/Pelj-1A6. Estimation of the Mass Flow Rate on the Basis of the Variation ofthe Speed of Rotationdmj=mj-1.dnj/Nj

1. An air conditioning installation for vehicle with engine furnishedwith an injection computer (42), the installation comprising arefrigerant closed circuit comprising a compressor (14), a condenser(11), a relief valve (12) and an evaporator (13), the condenserreceiving a stream of air passing through an electric fan assembly (15),as well as an electronic control device (401) intended to interact withthe refrigerant closed circuit (10) and the injection computer (42),characterized in that it comprises measurement facilities making itpossible to establish: a first value relating to the temperature of theexternal air stream at the inlet of the condenser (Taek), a second valuerelating to the pressure at the outlet of the compressor, termed thehigh pressure (HP), a third value relating to the pressure at the inletof the compressor, termed the low pressure (LP), the electronic controldevice (401) being able to implement the solving of a linear equation,relating the mass flow rate of the refrigerant (m) to the valuesmeasured by the first and the second measurement facility so as tocalculate an estimate of a quantity relating to the refrigerant and toestimate, on the basis of this quantity, of the measurements deliveredby said measurement facilities and of the information items transmittedby the injection computer (42), the power absorbed by the compressor(14).
 2. The air conditioning installation as claimed in claim 1,characterized in that the compressor is a mechanical compressor and inthat the quantity calculated by the electronic control device is themass flow rate of the refrigerant (m).
 3. The air conditioninginstallation as claimed in claim 1, characterized in that the compressoris an electric compressor and in that the quantity calculated by theelectronic control device is the high pressure (HP) of the refrigerant.4. The air conditioning installation as claimed in claim 1,characterized in that the first measurement facility is a probe (24),placed between the electric fan assembly (15) and the condenser (11),which delivers a measurement of the value of the temperature of theexternal air stream at the inlet of the condenser (Taek).
 5. The airconditioning installation as claimed in claim 4, characterized in thatthe first measurement facility is a probe linked to the injectioncomputer (42) which delivers a measurement of the value of thetemperature of the external air stream (Text).
 6. The air conditioninginstallation as claimed in claim 5, characterized in that the electroniccontrol device (401) is able to calculate an estimate of the value ofthe temperature of the external air stream at the inlet of the condenser(Taek), on the basis of the value of the temperature of the external air(Text) and of the value of the forward speed (Va) of the vehicle thatare delivered by the injection computer (42).
 7. The air conditioninginstallation as claimed in claim 1, characterized in that the secondmeasurement facility is a probe (23) placed at the inlet of thecondenser (11) directly within the refrigerant, which delivers ameasurement of the value of the condensation temperature (Tk).
 8. Theair conditioning installation as claimed in claim 7, characterized inthat the electronic control device (401) is able to calculate the valueof the high pressure (HP) on the basis of the value of the condensationtemperature (Tk) delivered by the second measurement facility.
 9. Theair conditioning installation as claimed in claim 1, characterized inthat the second measurement facility is a sensor (123), placed betweenthe outlet of the compressor (14) and the inlet of the condenser (11),which directly measures the instantaneous value of the high pressure(HP).
 10. The air conditioning installation as claimed in claim 1,characterized in that the second measurement facility is a sensor (123),placed between the outlet of the condenser (11) and the inlet of therelief valve (12), intended to directly measure the instantaneous valueof the high pressure (HP).
 11. The air conditioning installation asclaimed in one of claims 9 and 10, characterized in that the electroniccontrol device (401) is able to calculate the value of the condensationtemperature (Tk), on the basis of the instantaneous value of the highpressure (HP) delivered by the second measurement facility.
 12. The airconditioning installation as claimed in claim 1, characterized in thatthe third measurement facility is a probe (122), placed in the vanes ofthe evaporator (13), which delivers a measurement of the instantaneousvalue of the evaporation temperature.
 13. The air conditioninginstallation as claimed in claim 1, characterized in that the thirdmeasurement facility is a probe (122), placed within the refrigerant,which delivers a measurement of the instantaneous value of theevaporation temperature.
 14. The air conditioning installation asclaimed in one of claims 12 and 13, characterized in that the electroniccontrol device is able to calculate the value of the low pressure (LP)on the basis of the instantaneous value of the evaporation temperaturedelivered by the second measurement facility.
 15. The air conditioninginstallation as claimed in claim 1, characterized in that the thirdmeasurement facility is a sensor (22), placed between the evaporator(13) and the compressor (14), which directly delivers a measurement ofthe instantaneous value of the low pressure (LP).
 16. The airconditioning installation as claimed in claim 2, taken in combinationwith one of claims 4 to 15, characterized in that the electronic controldevice (401) is able to calculate an estimate of the mass flow rate ofthe refrigerant on the basis of the values measured by the first and thesecond measurement facility and of two information items relating to theoperation of the vehicle, that are transmitted by the injection computer(42).
 17. The air conditioning installation as claimed in claim 16,characterized in that the information items relating to the operation ofthe vehicle are related to the forward speed of the vehicle and to thevoltage of the electric fan assembly.
 18. The air conditioninginstallation as claimed in claim 16, characterized in that theelectronic control device (401) is able to calculate the power absorbedby the compressor on the basis of the calculated estimate of the massflow rate, of the values measured by the second and the thirdmeasurement facility, and of information items relating to the operationof the vehicle, that are delivered by the injection computer (42). 19.The air conditioning installation as claimed in claim 18, characterizedin that the information items relating to the operation of the vehicleare related to the speed of rotation of the compressor.
 20. The airconditioning installation as claimed in claim 3, taken in combinationwith one of claims 4 to 15, characterized in that the electronic controldevice (401) is able to calculate an estimate of the high pressure (HP)of the refrigerant on the basis of the value measured by the firstmeasurement facility, of the value of the mass flow rate of therefrigerant and of two information items relating to the operation ofthe vehicle, that are transmitted by the injection computer (42). 21.The air conditioning installation as claimed in claim 20, characterizedin that the information items relating to the operation of the vehicleare related to the forward speed of the vehicle and to the voltage ofthe electric fan assembly.
 22. The air conditioning installation asclaimed in claim 20, characterized in that the electronic control device(401) is able to calculate the power absorbed by the compressor on thebasis of the estimate of the high pressure (HP) calculated, of the valuemeasured by the third measurement facility, and of information itemsrelating to the operation of the vehicle, that are delivered by theinjection computer (42).
 23. The air conditioning installation asclaimed in claim 22, characterized in that the information itemsrelating to the operation of the vehicle are related to the speed ofrotation of the compressor.
 24. The air conditioning installation asclaimed in claims 20 to 23, characterized in that the electronic controldevice is capable, for a given starting state, of iterativelycalculating values of the power absorbed by the compressor, on the basisof values of the high pressure corresponding to small chosen variationsof the speed of rotation so as to estimate the maximum speed ofrotation.
 25. The air conditioning installation as claimed in claim 24,characterized in that the values of the high pressure are calculated onthe basis of the successive values of the mass flow rate of therefrigerant, which values are calculated as a function of the smallvariations of the speed of rotation.
 26. The air conditioninginstallation as claimed in claim 25, characterized in that the startingstate comprises the values of the high pressure (HP) and of the lowpressure (LP), measured by the second and the third measurementfacility, corresponding to an initial speed of rotation.